bellydancing. I haven't done it in a while but I was into it for years. It's a lot of fun and oddly empowering. I also liked kickboxing and yoga but the bellydancing was easier to keep up with because there is a lot to learn and it keeps evolving- kindof the way contemporary dance has a momentum.
In addition, I can't wait for the nicer weather so I can get back to my power walks. I do between 5km and 10km each day along Lake Ontario. On rainy days, I go on my treadmill and elliptical, but that's not as much fun as walking beside the lake in the sun.